Interactions Between The Human Immune System And Antigen

Neurological Disorders And Stroke

Investigators

Linked publications & trials

Abstract

This project examines the immunological mechanisms which involved in the pathogenesis of autoimmune- and infectious diseases of the central nervous system such as multiple sclerosis (MS) and chronic Lyme disease. We characterize the fine specificity, function and phenotype of T lymphocytes in the above diseases. These experiments allow a better understanding of the foreign antigens that may trigger autoimmune responses in MS and also of their function with respect to cytokine secretion and chemokine receptor expression. Based on this knowledge the project attempts to develop both specific immunomodulatory treatments such as altered peptide ligands (APL) or therapies that influence immune recognition in MS in a broader way. Examples of the latter are the humanized antibody against the interleukin-2 receptor alpha chain (Zenapax) or the phosphodiesterase type IV inhibitor Rolipram. The trial with the APL peptide has been concluded, and the data published. The clinical trials with Zenapax and Rolipram are both supported through bench-to-bedside proposals. Treatment of relapsing-remitting MS patients failing interferon-beta with Zenapax has been well tolerated and successful, i.e. the primary outcome has been met. Clinicial testing of Rolipram has been stopped due to lack of efficacy and necessary changes of trial design. Mechanistic studies along the experimental trials are ongoing and have e.g. delineated that Zenapax acts primarily via expansion of immunoregulatory NK cells. These studies will help us to understand better the complex mechanism of action of these compounds and eventually also the disease pathogenesis itself. All the clinical projects are being pursued in close collaboration with the Neurological Disease Section Section/Office of the Chief under Henry F. McFarland, M.D. Another important project, which is currently being pursued at NIB, NINDS, NIH, addresses the question which foreign antigens, e.g. viruses or bacteria, may trigger the initiation or exacerbations of disease via a mechanism referred to as molecular mimicry. This concept refers to cross-recognition between autoantigens, e.g. derived from the myelin sheath, and antigens derived from foreign agents. For this purpose, we currently employ a novel methodology called combinatorial peptide libraries in the positional scanning format (ps-SCL) together with bioinformatic approaches to identify the entire spectrum of stimulatory ligands for autoreactive T cell clones derived from MS patients. In brief, we test T cell clones with ps-SCL, which represent highly complex mixtures of trillions of peptides, and deduce stimulatory peptide sequences from these assays before we screen the databases of all known protein sequences for potential stimulatory peptides. We are currently in the process of developing this methodology further and anticipate that the combination of ps-SCL and biometric data analysis will lead to advances in the identification of target antigens for autoimmune diseases, but also for tumor-specific lymphocytes or T cells that are involved in infectious disease. As an example for the latter, our data for organ-infiltrating T cells in chronic nervous system Lyme disease already suggest that the immune response in the chronic stage of the disease is directed against tissue autoantigens and that this process is thus very similar to an autoimmune disease. Currently, we also develop molecular biology strategies, i.e. the expression of cDNA clones from MS brain in a special eukaryotic expression system, for the identification of novel proteins that are expressed in MS brains and serve as targets for the autoimmune response. New projects include: The migration and differentiation of neural stem cells into glial/neural cells. Integration of immunological studies, MRI, clinical examination, expression profiling and proteomics for the stratification of MS subtypes.